An electric power assist steering system for a wheeled vehicle includes a rotating electric machine which is combined together with a control device (See Patent Documents 1-15, for reference). Usually, the control device is arranged on an anti-output shaft side of the rotating electric machine (See Patent Document 1, for reference). In the control device, there is provided a power module for supplying driving current and a heat sink for absorbing heat generated by the power module. The power module and the heat sink are disposed on the outside of a case of the rotating electric machine. The heat sink is connected with the surrounding portion of the case of the rotating electric machine by way of an intermediate member, where the heat sink is within the case in outer diameter. On a motor frame, there is mounted a bearing which supports the anti-output shaft side of the rotating electric machine.
As in a rotating electric machine which is combined with a control device, a control substrate and a heat sink are arranged in the control device (See Patent Document 2, for reference). A rotary sensor for detecting a rotational angle of a rotor is disposed along a shaft direction and faces a permanent magnet of sensor use. The permanent magnet of sensor use is held at the end portion of the anti-output shaft side of the rotating electric machine. The heat sink is in contact with the switching elements of a drive circuit for the rotating electric machine. A bearing of the anti-output shaft side is arranged on the heat sink. The small-sizing of a shaft length and the reduction in the number of components are considered.
In the configuration mentioned above, a bearing of the anti-output shaft side is arranged in a heat sink. Efforts are made to contract the length of a shaft and to reduce the number of components. Noise reduction coils, condensers and others are arranged between the heat sink and the control substrate. Thereby, the distance from the bearing of the anti-output shaft side to the control substrate is large. The rotating electric machine may be increased in size and weight, when the rotating electric machine is large in shaft length. Further, the noise reduction coils, the condensers and others are arranged on a heat sink, in such a way that they are embedded in the heat sink. Accordingly, the volume of the heat sink is reduced and the heat capacity of the heat sink is decreased. Moreover, the distance between the heat sink and the control substrate becomes large, when the heat sink is in contact with the switching elements of the control substrate and absorbs heat produced. Accordingly, a protrusion portion becomes large in length and the electric rotation machine may have increased size and weight.